1. Field of the Invention
This invention relates to a sewing apparatus with a cassette mount to which a thread cassette is detachably attached, and more particularly to a technique for performing different needle bar position changing control manners depending upon whether or not the thread cassette has been attached to the cassette mount when a needle bar position changing means has been operated.
2. Description of the Related Art
There has conventionally been proposed a sewing apparatus which includes a cassette mount to which a thread cassette accommodating a thread spool is detachably attached and in which a thread drawn from the thread cassette serves as a needle thread. In the sewing apparatus, the thread drawn from the thread cassette attached to the cassette mount is caught between a pair of thread tension discs of a thread tensioning mechanism. The thread extending downstream from the thread tension discs is caught on a needle thread take-up lever, and the thread extending downstream from the lever is passed through an eye of a sewing needle mounted on a needle bar.
It is desirable that the above-described sewing apparatus be provided with a threading mechanism for passing a thread drawn from the thread cassette attached to the cassette mount through an eye of a sewing needle. Furthermore, in order that the thread may be passed through the needle eye, the threading mechanism needs to be operated while a needle bar vertically moved by a needle bar vertically moving mechanism is stopped at an upper stop position.
On the other hand, the assignee of this application filed a Japanese patent application assigned with Application No. 2002-91558 and relating to a sewing apparatus including a thread carrying mechanism and a threading mechanism each operated in synchronization with attachment of the thread cassette to the cassette mount. The thread drawn from the thread cassette is automatically passed through the needle eye by the thread carrying mechanism and threading mechanism. In the disclosed sewing apparatus, the thread drawn from the thread cassette is caught and carried near the needle eye by the thread carrying mechanism, and the carried thread is caught by the threading mechanism to be passed through the needle eye.
In the above-described sewing apparatus, the threading mechanism is operated in synchronization with the operation of attaching the thread cassette to the cassette mount. Accordingly, in order that passing the thread through the needle eye may be realized by the threading mechanism, the thread cassette needs to be attached to the cassette mount while the needle bar is stopped at an upper stop position.
Cloth to be sewn is set to the sewing apparatus while the needle bar is stopped at the upper stop position. While the needle bar is stopped at a lower stop position, the thread is stuck into the set cloth so that a positional relationship is maintained between the cloth and needle. The cloth can be turned about the needle in order that a sewing direction may be changed. In conventional sewing apparatus, a needle up-down key is provided which is operated to change the position of the needle bar between the upper and lower stop positions alternately. Furthermore, there are some conventional sewing machines in which the threading mechanism is not operated when the needle bar has a height lower than a predetermined one.
When a conventional sewing machine with the cassette mount to which the thread cassette is detachably attached includes a threading mechanism, a user has a difficulty in moving the needle bar to the upper stop position to stop it there by operating a spindle pulley or the like while viewing the needle bar. Threading sometimes fails when the threading mechanism is operated although the needle bar is stopped at any position other than the upper stop position. The threading mechanism or the like would be damaged depending in certain conditions. A trial-and-error operation would be required at many times until the needle bar reaches a suitable height. As a result, the working efficiency would be reduced.
In the sewing apparatus disclosed in aforesaid Japanese patent application No. 2002-91558, the thread cassette needs to be attached to the cassette mount while the needle bar is stopped at the upper stop position. The above-described problems also apply to the disclosed sewing apparatus. When threading has failed, the thread cassette would need to be re-attached to the cassette mount, and the preparation for threading needs to be re-executed, thereby resulting in troubles.
Furthermore, the aforesaid needle up-down key may be applied to the sewing apparatus with the cassette mount to which the thread cassette is attached. However, the needle bar is changed between the upper and lower stop positions alternately every time the needle up-down key is operated. Accordingly, even when the needle up-down key is operated before threading so that the needle bar is located at the lower stop position, the threading mechanism would sometimes be operated (or the thread cassette would be attached to the cassette mount in the sewing apparatus disclosed in Japanese patent application No. 2002-91558).
The location of the needle bar needs to be confirmed in order that the user may operate the needle up-down key to stop the needle bar at the upper stop position. Furthermore, in certain cases, the needle up-down key needs to be operated twice to stop the needle bar at the upper stop position. Thus, load applied to the user is increased and accordingly, the position change is troublesome. In order that the sewing apparatus may be improved in the convenience thereof, it is desirable that the needle up-down key be operated to change the needle bar between the upper and lower stop positions alternately.
Therefore, an object of the present invention is to provide a sewing apparatus in which when a needle bar position changing means is operated, the needle bar is changed to the upper or lower stop position according to the position at the time of operation of the needle bar position changing means in the case where the thread cassette is attached to the cassette mount, and the needle bar is changed only to the upper stop position when the thread cassette is unattached to the cassette mount, whereupon the thread cassette can desirably be attached to the cassette mount.
The present invention provides a sewing apparatus comprising, a needle bar, a needle bar vertically moving mechanism vertically moving the needle bar, a needle bar position changing operation unit operated via the needle bar vertically moving mechanism to change a vertical position of the needle bar, a thread cassette having a thread accommodating section accommodating a supply of thread, a cassette mount to which the thread cassette is detachably attached, a cassette detector detecting the thread cassette attached to the cassette mount, and a needle bar position changing control unit. The needle bar position changing control unit controls the needle bar vertically moving mechanism so that in a case where the needle bar position changing unit has been operated, the needle bar is changed from an upper stop position to a lower stop position or from the lower stop position to the upper stop position according to a position of the needle bar at the time of operation of the needle bar position changing unit when the thread cassette is attached to the cassette mount according to a result of detection by the cassette detector. The needle bar position changing control unit further controls the needle bar vertically moving mechanism so that the needle bar is changed to the upper stop position irrespective of the position of the needle bar at the time of operation of the needle bar position changing unit when the thread cassette is unattached to the cassette mount according to the result of detection by the cassette detector.
When the presence or absence of the thread cassette attached to the cassette mount has been detected by the cassette detector and the needle bar position changing operation unit has been operated, the needle bar position changing control unit controls the needle bar vertically moving mechanism on the basis of the result of detection by the cassette detector. In the control, when the thread cassette is attached to the cassette mount, the needle bar is changed from the upper stop position to the lower stop position or from the lower stop position to the upper stop position according to the position of the needle bar at the time of operation of the needle bar position changing unit. When the thread cassette is unattached to the cassette mount, the needle bar is changed to the upper stop position irrespective of the position of the needle bar at the time of operation of the needle bar position changing unit.
A space for set and removal of cloth to and from the sewing apparatus is defined below the needle bar when the needle bar is at the upper stop position. When the needle bar is at the lower stop position, the needle is stuck into cloth set to the sewing apparatus so that a positional relationship is maintained between the cloth and needle. In a case where the thread cassette has been attached to the cassette mount, the needle bar is changed between the upper and lower stop positions alternately every time the user operates the needle bar position changing operation unit once. On the other hand, when the thread cassette has not been attached to the cassette mount, the needle bar need not be changed to the lower stop position. Accordingly, the needle bar is changed to the upper stop position irrespective of the position of the needle bar when the user operates the needle bar position changing operation unit once.
The needle bar position changing control unit preferably controls the needle bar vertically moving mechanism so that when the thread cassette is unattached to the cassette mount according to the result of detection by the cassette detector and the needle bar is at the upper stop position, the needle bar is changed to the lower stop position once and subsequently to the upper stop position.
The sewing apparatus preferably further comprises a threading mechanism passing the thread drawn from the thread cassette through an eye of a needle attached to the needle bar when the thread cassette is attached to the cassette mount. In this case, the upper stop position is determined so that the threading mechanism is operable to pass the thread drawn from the thread cassette through the needle eye.